Add database configuration source to the source stack

Summary:
Read configuration from the new database source.

This adds an extra MySQL connect + query to every page. They're very cheap so I think we can suffer them for now, but I'd like to put cache in front of this at some point. The difficulties are:

  - If we use APC, multi-frontend installs (Facebook) can't dirty it (major problem), and the CLI can't dirty it (fine for now, maybe a major problem later).
  - If we use Memcache, we need to add config stuff.
  - We could use APC in all non-Facebook installs if we can make it dirtyable from the CLI, but I don't see a reasonable way to do that.
  - We don't have any other caches which are faster than the database.

So I'll probably implement Memcache support at some point, although this is a lame excuse for it.

Test Plan: Added some config values via web UI, saw them active on the install.

Reviewers: btrahan, codeblock, vrana

Reviewed By: codeblock

CC: aran

Maniphest Tasks: T2221

Differential Revision: https://secure.phabricator.com/D4296

src/__phutil_library_map__.php

@@ -702,6 +702,7 @@ phutil_register_library_map(array(
     'PhabricatorConduitTokenController' => 'applications/conduit/controller/PhabricatorConduitTokenController.php',
     'PhabricatorConfigAllController' => 'applications/config/controller/PhabricatorConfigAllController.php',
     'PhabricatorConfigController' => 'applications/config/controller/PhabricatorConfigController.php',
+    'PhabricatorConfigDatabaseSource' => 'infrastructure/env/PhabricatorConfigDatabaseSource.php',
     'PhabricatorConfigDefaultSource' => 'infrastructure/env/PhabricatorConfigDefaultSource.php',
     'PhabricatorConfigDictionarySource' => 'infrastructure/env/PhabricatorConfigDictionarySource.php',
     'PhabricatorConfigEditController' => 'applications/config/controller/PhabricatorConfigEditController.php',
@@ -2089,6 +2090,7 @@ phutil_register_library_map(array(
     'PhabricatorConduitTokenController' => 'PhabricatorConduitController',
     'PhabricatorConfigAllController' => 'PhabricatorConfigController',
     'PhabricatorConfigController' => 'PhabricatorController',
+    'PhabricatorConfigDatabaseSource' => 'PhabricatorConfigProxySource',
     'PhabricatorConfigDefaultSource' => 'PhabricatorConfigProxySource',
     'PhabricatorConfigDictionarySource' => 'PhabricatorConfigSource',
     'PhabricatorConfigEditController' => 'PhabricatorConfigController',

src/infrastructure/env/PhabricatorConfigDatabaseSource.php

@@ -0,0 +1,23 @@
+<?php
+
+final class PhabricatorConfigDatabaseSource
+  extends PhabricatorConfigProxySource {
+
+  public function __construct($namespace) {
+    $config = $this->loadConfig($namespace);
+    $this->setSource(new PhabricatorConfigDictionarySource($config));
+  }
+
+  public function isWritable() {
+    // While this is writable, writes occur through the Config application.
+    return false;
+  }
+
+  private function loadConfig($namespace) {
+    $objects = id(new PhabricatorConfigEntry())->loadAllWhere(
+      'namespace = %s AND isDeleted = 0',
+      $namespace);
+    return mpull($objects, 'getValue', 'getConfigKey');
+  }
+
+}

src/infrastructure/env/PhabricatorEnv.php

@@ -102,8 +102,6 @@ final class PhabricatorEnv {
 
 
   private static function initializeCommonEnvironment() {
-    $env = self::getSelectedEnvironmentName();
-
     self::buildConfigurationSourceStack();
 
     PhutilErrorHandler::initialize();
@@ -149,6 +147,12 @@ final class PhabricatorEnv {
     $stack->pushSource(
       id(new PhabricatorConfigLocalSource())
         ->setName(pht("Local Config")));
+
+    // NOTE: This must happen after the other sources are pushed, because it
+    // will draw from lower-level config to bootstrap itself.
+    $stack->pushSource(
+      id(new PhabricatorConfigDatabaseSource('default'))
+        ->setName(pht("Database")));
   }
 
   public static function getSelectedEnvironmentName() {